Janice M. Santiago-O’Farrill

DIRAS3 Inhibits Ovarian Cancer Cell Growth by Blocking the Fibronectin-Mediated Integrin β1/FAK/AKT Signaling Pathway

Autophagy is a crucial cellular process responsible for sustaining homeostasis through the degradation and recycling of proteins and organelles, providing energy during amino acid starvation and hypoxia. In cancer, autophagy can either inhibit tumor growth or support cancer cell survival. Our previous studies have shown that re-expression of the tumor suppressor gene DIRAS3 inhibits growth of ovarian cancer cells, promotes autophagic cell death in vitro, and induces tumor dormancy in vivo. Growth factors and extracellular matrix (ECM) components can, however, inhibit DIRAS3-induced autophagic cell death. This study explores whether fibronectin (FN) can counteract the growth inhibition induced by DIRAS3 in ovarian cancer cells. FN was found to inhibit DIRAS3-induced autophagy and to partially rescue ovarian cancer cells from DIRAS3-induced cell death while reducing DIRAS3-induced inhibition of p-FAK and p-AKT. Inhibiting FAK with defactinib in ovarian cancer cells enhanced DIRAS3-induced autophagy and cell death. Re-expression of DIRAS3 and treatment with defactinib produced tumor regression in xenograft models. Our findings suggest that ECM components in the tumor microenvironment like FN enhance the activities of β1 integrin, FAK, and AKT to inhibit DIRAS3-induced autophagic cell death, thereby promoting ovarian cancer cell survival.

Crizotinib Enhances PARP Inhibitor Efficacy in Ovarian Cancer Cells and Xenograft Models by Inducing Autophagy

Abstract Poly (ADP-ribose) polymerase inhibitors (PARPi) can encounter resistance through various mechanisms, limiting their effectiveness. Our recent research showed that PARPi alone can induce drug resistance by promoting autophagy. Moreover, our studies have revealed that anaplastic lymphoma kinase (ALK) plays a role in regulating the survival of ovarian cancer cells undergoing autophagy. Here, we explored whether the ALK-inhibitor crizotinib could enhance the efficacy of PARPi by targeting drug-induced autophagic ovarian cancer cell and xenograft models. Our investigation demonstrates that crizotinib enhances the anti-tumor activity of PARPi across multiple ovarian cancer cells. Combination therapy with crizotinib and olaparib reduced cell viability and clonogenic growth in two-olaparib resistant cell lines. More importantly, this effect was consistently observed in patient-derived organoids. Furthermore, combined treatment with crizotinib and olaparib led to tumor regression in human ovarian xenograft models. Mechanistically, the combination resulted in increased levels of reactive oxygen species (ROS), induced DNA damage, and decreased the phosphorylation of AKT, mTOR, and ULK-1, contributing to increased olaparib-induced autophagy and apoptosis. Notably, pharmacologic, or genetic inhibition or autophagy reduced the sensitivity of ovarian cancer cell lines to olaparib and crizotinib treatment, underscoring the role of autophagy in cell death. Blocking ROS mitigated olaparib/crizotinib-induced autophagy and cell death while restoring levels of phosphorylated AKT, mTOR and ULK-1. These findings suggest that crizotinib can improve the therapeutic efficacy of olaparib by enhancing autophagy. Implications: The combination of crizotinib and PARPi presents a promising strategy, that could provide a novel approach to enhance outcomes for patients with ovarian cancer.